Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
Title of Invention:
A MOULD FOR THE INJECTION MOULDING OF ELEMENTS WITH UNDERCUTS MADE OF PLASTIC
MATERIAL, WITH AN INTEGRATED EJECTION SYSTEM
Technical Field
[ 1 ] The present invention refers to a mould for the injection moulding of
elements made
of plastic material.
[2] More precisely, the present invention refers to a mould for the injection
moulding of
vehicles bodywork portions made of plastic material.
[3] Even more precisely, the present invention refers to a mould for the
injection
moulding of bumpers made of plastic material.
[4] The present invention also refers to a moulding apparatus comprising the
aforesaid
mould.
Background Art
Background Art
[5] The use of components made of plastics through injection moulding is very
widespread, particularly in the automotive sector.
[6] The injection moulding is commonly carried out inside apparatuses
comprising a
mould consisting of a puncher and of a matrix, movable relative to each other,
having
surfaces shaped so as to form, when coupled, a cavity having the shape of the
piece to
be moulded. These two elements, puncher and matrix, are connected to the corre-
sponding bottom plates, plane and mutually parallel, that, in turn, are
connected to a
manufacturing press; depending on the press operative needs, the mould can be
vertically or horizontally arranged with respect to the press moulding axis
that, in turn,
can be horizontal or vertical, preferably horizontal, with respect to the
press ground
support surface.
[7] A removal system is further provided to allow the removal of the moulded
piece, said
removal system being movable and equipped with numerous and complex handling
components for the moulded piece.
[8] An example of an injection moulding apparatus according to the above-
mentioned
known art is that described in the Italian Patent application No.
MI2005A001979; in
particular, this apparatus is provided with a ring-closed removal system,
arranged
around the puncher and movable with respect to both the corresponding bottom
plate
and the puncher itself.
[9] The aforesaid kind of apparatuses has the drawback to provide a closed
structure,
hardly inspectable and maintainable.
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[10] Moreover, the aforesaid kind of apparatuses has the drawback to provide
slidings of
the removal system with respect to the puncher and among the movable parts of
the
puncher itself, which can cause seizings and resulting operation breaks.
[11] Finally, the aforesaid kind of apparatuses has the drawback to provide
components
that can cause bends due to the injection pressure and, consequently, create
defects in
the moulded piece; an example of said components is represented, in the
specific case
of the above-mentioned application, by a closed frame interposed between the
movable
parts and the puncher, while, more generally, by inclined columns that,
resting on the
bottom plate, allow the movement of the movable parts and are significantly
bending
stressed.
[12] In a continuously developing industrial sector, it is necessary to
guarantee the ap-
paratuses operation continuity and the process times reduction, to allow easy
and quick
maintenance actions, to assure the system stiffness and the required quality
levels.
[13] It appears therefore evident that the need still exists for a solution
that, differently
from the apparatuses of the known art above illustrated, allows to achieve the
aforesaid
operative and maintenance performances.
[14] Furthermore, the need exists for a solution that allows to achieve the
required quality
levels, specifically by automotive industries.
Disclosure of Invention
Summary of the Invention
[15] The present invention intends to overcome drawbacks and limits of the
solutions of
the prior art previously depicted and to meet the still unsatisfied need for a
solution
that allows to achieve better operative and maintenance performances as well
as the
required optimum quality levels, specifically by automotive industries.
[16] This object is achieved with the mould, and with the relevant apparatus,
for the
moulding of elements, particularly of vehicles bodywork portions, more
particularly of
bumpers, made of plastic material according to the invention that, by
advantageously
providing a mould with an innovative removal system, allows to achieve better
operative and maintenance performances as well as the required optimum quality
levels, specifically by automotive industries.
[17] More precisely, the mould for moulding according to the invention
comprises a
puncher, a matrix and a removal system, and it is characterised in that said
removal
system comprises internal transversal bars and external longitudinal bars
conveniently
assembled and connected to each other so as to form a single and stiff, but
not closed,
body, which is able to guarantee the handling of the moulded piece.
[18] In this way, the mould, and the relevant apparatus, for moulding
according to the
invention assures the reduction of moulding times because of more compact
sizes and
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limited handling strokes, the reduction of the mould maintenance costs as a
result of
the visibility of the areas subjected to wear and an optimum aesthetic quality
of the
manufactured products, especially after painting, thanks to the stiffness of
the removal
system structure.
Brief Description of the Drawings
[19] The following figures, given by way of non limiting example, help to
illustrate the
present invention, a preferred embodiment of which will be afterwards
described in
detail:
[20] - FIG. 1 is a longitudinal section view of the moulding apparatus
according to the
invention;
[21] - FIG. 2 is an enlarged detail of FIG. 1;
[22] - FIG. 3 is a view along section A-A of FIG. 2;
[23] - FIG. 4 is a transversal section view of the moulding apparatus
according to the
invention;
[24] - FIG. 5 is a top plan view of the removal system of the mould according
to the
invention;
[25] - FIG. 6 is a perspective view of the removal system of the mould
according to the
invention;
[26] - FIG. 7 is a perspective view of an enlarged detail of the removal
system of the
mould according to the invention, in which a first variant of the support of
said
removal system is represented;
[27] - FIG. 8 is an enlarged detail of FIG. 7 showing a second variant of the
support of the
removal system according to the invention;
[28] - FIG. 9 is a flow diagram illustrating in detail the main operation
steps of the
moulding apparatus according to the invention;
[29] - FIG. 10 is an exploded perspective view of an enlarged detail of the
moulding
apparatus according to the invention in a specific application;
[30] - FIG. 11 is a perspective view of an element made of plastic material
obtained with
the moulding apparatus according to the invention.
Detailed description of a Preferred Embodiment
[31]
[32] With reference to FIG. 1, it is to be noticed that the moulding apparatus
1 according
to the invention comprises a mould 3 comprising a puncher 2, consisting of an
upper
portion, or puncher as properly said, 2a and of a lower portion, or puncher-
holder, 2b,
and of a matrix 4.
[33] Said puncher 2 and said matrix 4 have surfaces shaped so as to form, when
coupled,
a cavity 5 having the shape of the element to be moulded, hereinafter moulded
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element, 7 and into which the melted plastic material will be injected under
pressure.
[34] Said puncher 2 and said matrix 4 are connected to corresponding puncher
bottom
plate 6 and matrix bottom plate 8, respectively, plane and mutually parallel,
said
bottom plates being connected, in turn, to a manufacturing press of the known
type
(not shown); depending on the press operative needs, the mould 3 can be
vertically or
horizontally arranged with respect to the press moulding axis that, in turn,
can be
horizontal or vertical, preferably horizontal, with respect to the press
ground support
surface.
[35] The closing and opening movements of the mould 3, and consequently the
approach
and separation movements of said puncher 2 and of said matrix 4, are guided by
said
press; depending on the kind of chosen press, said puncher 2 and said matrix 4
can be
movable relative to each other, or only said puncher 2 or only said matrix 4
can move,
the other one, i.e. the matrix 4 or the puncher 2, respectively, keeping the
rest position.
[36] As mentioned above, said puncher 2 consists of two portions and said
puncher as
properly said 2a is supported by said puncher-holder 2b that is fastened to
the puncher
bottom plate 6; on the contrary, said matrix 4 is directly fastened to the
matrix bottom
plate 8.
[37] Said puncher bottom plate 6 and said matrix bottom plate 8 rest on
corresponding
press surfaces and define reference press-planes P1 and P2, respectively.
[38] Depending on the kind of chosen press, the press-planes P1 and P2 can be
re-
ciprocally movable but, preferably the matrix press-plane P1 keeps still while
the
puncher press-plane P2 moves along the direction of the moulding axis, which
can be
horizontal or vertical, preferably horizontal, with respect to the press
ground support
surface.
[39] With reference to FIG. 2, it is to be noticed that inside the puncher as
properly said
2a there are movable parts such as, in particular, insertions in the central
part of the
puncher, ore movable slices, 22 and one or more insertions superimposed and/or
laterally arranged relative to the slices, or upper sliders, 24; furthermore,
there is an
insertion, or pusher, 26 that, thanks to its high thermal conductivity,
releases heat and
cooperates to the uniform cooling of the piece, which is an important
condition to
avoid deformation of the plastic material and superficial defects.
[40] It is important to point out that, according to the present invention,
said movable
slices 22 directly rest on the puncher 2, specifically on the puncher-holder
2b.
[41] The side of the body of the puncher 2 has an inclination of an angle 0,
whose value
preferably ranges between 10 and 20 , with respect to the moulding direction
Z,
which is also the direction of closing and opening of the mould 3.
[42] In order to slide during opening and closing of the mould 3, the movable
slices 22 are
connected to the inclined side of the puncher 2 through first T-guides 10, as
shown in
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FIG. 3; also during the removal of the moulded piece 7, the movable slices 22
slide on
the first T-guides 10 moving back relative to the puncher 2.
[43] It is important to point out that said first T-guides 10, provided in the
present
invention unlike the known art solutions, solve the problem of the bends to
which the
inclined columns resting on the bottom plate are subjected.
[44] Said first T-guides 10, preferably made of bronze, are fastened to the
puncher 2 by
known methods and are able to slide in appropriate corresponding seats
obtained in the
slices 22.
[45] In order to facilitate the adjusting of the movable slices 22, said first
T-guides 10 are
not directly placed in contact with the puncher 2, but first small plates 11
are provided,
made of cemented and tempered steel and positioned between the first T-guides
10 and
the puncher 2.
[46] The first T-guides 10 are inclined at an angle lower of 0 and 5 ,
preferably of 1 ,
than the angle 0 of the side of the puncher 2.
[47] The moulding apparatus 1 further comprises a removal system 9 to remove
the
moulded piece 7 from the mould 3; said removal system 9 is supported by the
puncher-
holder 2b and it is movable relative to the puncher 2.
[48] Making reference to FIG. 4, it is to be noticed that said removal system
comprises
internal transversal bars 91 (also visible in FIGG. 1 and 2) and external
longitudinal
bars 93.
[49] Always with reference to FIG. 4, it is to be noticed that the apparatus 1
further
comprises one or more guide columns 19 (also visible in FIG. 1) required for
centring
and guiding said removal system 9 during its stroke, second small plates 21,
also made
of cemented and tempered steel, resting on the puncher 2, and screws 23
connecting
said internal transversal bars 91 and said external longitudinal bars 93.
[50] Said removal system 9, which is the innovative component compared with
the known
art solutions, will be now disclosed in detail by making reference to FIGG. 5
and 6.
[51] Said internal transversal bars 91 and said external longitudinal bars 93
are con-
veniently assembled and connected to each other, for instance through screws
23 or
other known means such as fastening allen screws and centring pins, so as to
form a
single and stiff body, which is open; said internal transversal bars 91 and
said external
longitudinal bars 93 guarantee the handling of the moulded element 7, as will
be il-
lustrated afterwards.
[52] Preferably, said internal transversal bars 91 and said external
longitudinal bars 93 are
made of high-strength steel.
[53] The sizing of the bending-resistant section of the external longitudinal
bars 93 is of
particular importance, said external longitudinal bars 93 being stressed by
the weight
of the whole apparatus as well as by the friction due to the slidings of the
movable
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parts, specifically of the movable slices 22 and of the upper sliders 24.
[54] The optimum area of the bending-resistant section ranges between 50 cm2
and 200
cm2, and it is preferably of 100 cm2.
[55] As mentioned above, the centring of said external longitudinal bars 93 is
guaranteed
by one or more, preferably four, guide columns 19 provided with relevant
bronze
buckles (not shown); said guide columns 19 also act as fixed supports of said
external
longitudinal bars 93 to support the upper sliders 24, which are not subjected
to
translations, when this is required depending on the kind of the moulded piece
7.
[56] Said guide columns 19 are preferably made of steel.
[57] With reference to FIGG. 4 and 6 it is to be noticed that, in order to
facilitate the
sliding of the external longitudinal bars 93, it is necessary to provide said
second small
plates 21, cemented and tempered, that rest on the puncher-holder 2b and are
screwed
to the external longitudinal bars 93; said second small plates 21 cooperate
with said
guide columns 19 to facilitate said sliding particularly when the mould 3 is
hori-
zontally arranged.
[58] Again referring to FIG. 6, the movement of the removal system 9 is
assured by an
array of hydraulic cylinders 33 operating the movable parts 22, 24 inside the
upper
portion 2a of the puncher 2; as an alternative to or in combination with said
hydraulic
cylinders, mechanical jumpers can be used.
[59] Said array of hydraulic cylinders 33 consists of one or more, preferably
four, units,
preferably arranged two by two on the long sides of the apparatus; said four
hydraulic
cylinders 33, in the illustrated embodiment, are controlled by a system of
micro-
switches interfaced with the manufacturing press but, obviously, other control
systems
known to the person skilled in the art can be used.
[60] The connection between said cylinders 33 and the removal system 9 is made
through
a system 70, preferably a fork, that can be removed from the mould 3 by
operating
proper fastening means 73, for instance screws; other equivalent solutions
known to
the person skilled in the art can be applied as an alternative to the one
chosen for the
preferred embodiment herein illustrated.
[61] It is important to point out that the aforesaid arrangement allows to
easily access the
removal system 9, thus simplifying the maintenance operations.
[62] One or more, preferably four, first supports 12, to which the movable
slices 22 are
connected, are arranged at the ends of the external longitudinal bars 93 (as
it is visible
in FIG. 7); one or more, preferably four, second supports 32 for the
corresponding
upper sliders 24 are also provided.
[63] Said first supports 12 and second supports 32 are useful for making the
movable
parts 22, 24 solidly joined to the removal system 9.
[64] Depending on the requirements of the article to be produced, the present
invention
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provides two alternative variants as regards the sliding supports 12 of the
movable
slices 22.
[65] The first variant, visible in FIG. 7, provides that said supports 12
connecting the
external longitudinal bars 93 and the movable slice 22 are equipped, on the
parts
subjected to sliding, with third cemented and tempered small plates 13, which
allow
the movable slice 22 to rectilinearly slide towards the inside until it
reaches the stroke
necessary to remove the undercuts preventing the moulded element 7 from being
picked-up, i.e. until it comes into contact with the fixed portion of the
puncher 2.
[66] The second variant, visible in FIG. 8, provides that said supports 12 are
equipped
with bearings 14, which allow the movable slice 12 to slide according to an
inclined
direction; this version is to be preferred with compound movement directions
and
heavier movable slices; this variant has the specific advantage of making the
motion at
the beginning of the removal more uniform and fluid.
[67] These two solutions have an important feature in common with each other,
that is the
fact that the external longitudinal bars 93, which are subjected to sliding,
are arranged
in a way visible from the outside, this allowing both to visually monitor the
wear
thereof and to intervene for their replacement or maintenance without having
to dis-
assemble the mould 3.
[68] Again making reference to FIG. 7, it is to be noticed that the
translation motion of the
movable slices 22 is formed by a component along the Z direction, given by the
movement of the removal system 9 that, combined with the inclination of the
angle 0
preferably variable between 10 and 20 of the sides of the body of the
puncher 2,
gives a translation along the X direction, allowed by the four supports 12
being
present.
[69] More precisely, the shift direction of said movable slices 12 is given by
combining
the vertical movement of the removal system 9 and the movement of the first T-
guides
depending on the piece to be moulded 7.
[70] In other words, while the upper sliders 24 move only along the vertical
direction, the
movable slices 22 can either translate only along the horizontal direction or
have a
movement with both an horizontal and a vertical component, depending on the
moulded piece 7.
[71] As it can be appreciated, the removal system 9 according to the invention
has a
greater stiffness since the mechanical components are all in contact with one
other,
without any gap and, in particular, the movable slices 22 are in contact with
the
puncher 2.
[72] Moreover, contrary to the conventional moulds in which, as previously
highlighted,
there are inclined columns that, resting on the bottom plate, allow the
movement of the
movable parts, the present invention does not provide said inclined columns,
this
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allowing to increase the inclination angle, this, in turn, reducing the
puncher stroke of
about 35-45 %, with an evident positive consequence for the manufacturing
times,
which are thus reduced.
[73] It is necessary to specify that the removal system 9 according to the
present invention
is assembled separately and before being inserted between the upper portion 2a
and the
lower portion 2b of the puncher 2.
[74] More precisely, the assembly of the removal system 9 comprises the steps
of:
[75] - positioning the two external longitudinal bars 93,
[76] - arranging the internal transversal bars 91 perpendicularly to the
external lon-
gitudinal bars 93,
[77] - positioning the guide columns 19 on the internal transversal bars 91,
[78] - controlling the centring of said bars and mutually fastening them with
appropriate
means,
[79] - assembling the accessory components such as, for instance, the second
supports 32,
the second small plates 21, the third small plates 13, an so on,
[80] - accommodating the assembly thus obtained onto the puncher 2,
[81] - fastening the cylinders 33 and the first supports 12.
[82] After having assembled all the other components of the moulding apparatus
as well
as all the required adjustment and control systems, not listed in detail
because they are
common to the solutions according to the known art, the moulding manufacturing
cycle can be started.
[83] With reference to FIG. 9, the manufacturing cycle of the injection
moulded elements
7 made of plastic material is now described.
[84] First of all, puncher 2 and matrix 4 approach to each other until they
perfectly adhere
to form the cavity 5, that is until the mould 3 is completely closed;
depending on the
kind of the press, only either the puncher or the matrix will be shifted, or
both of them.
[85] Subsequently the tonnage operation is carried out, which essentially
consists in
adjusting the operative parameters depending on the kind of the piece to be
moulded 7.
[86] Then, the injection of the melted plastic material into said cavity 5 can
take place,
during which injection the mould 3 is closed and the movable slices 22 are
lined up
with the puncher 2.
[87] Thanks to the used removal system 9, when the mould 3 is closed for
injecting the
melted plastic material, the movable slices 22 rest on the puncher-holder 2b,
thus
avoiding the typical structural bendings of the conventional moulds, in which
said
movable slices are not centrally supported due to the gap between the bottom
plate and
the puncher.
[88] Once the injection of the plastic material is completed and the steps of
both holding
and cooling and solidifying the moulded piece 7 are finished, the opening of
the mould
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3 starts as a result of the opening of the press.
[89] The opening of the mould 3 can take place either previously or
simultaneously with
the first step of removal of the moulded piece 7.
[90] The opening of the mould 3 takes place simultaneously with the first step
of removal
of the moulded piece 7 when mould division, that is separation of the matrix
and of the
puncher, not in evidence on the visible external portion of the moulded piece
7, is
needed, that is when, for finishing aesthetic requirements of the moulded
piece 7, it is
necessary to move back the division point between matrix and puncher.
[91] At the end of the removal, the moulded piece 7 will have to be free from
restrainings
and ready for the complete removal, for instance through a robotised grasping
tool.
[92] Making now reference to FIGG. 10 and 11, a specific case of the invention
ap-
plication is shown.
[93] The specific application refers to the presence of undercuts 55 in the
fastening region
between a bumper 7 and the corresponding mudguard (not shown), as illustrated
in
FIG. 11.
[94] Making reference to FIG. 10, the movable slice 22 comprises a side lifter
15 in the
mudguard or side region, depending on whether it is a question of a mould for
a front
or a rear mudguard, comprising inclined second T-guides 18 allowing to
separate and
move back the region during the mould opening step as well as permitting the
removal
of the moulded piece 7; said second T-guides 18 slide inside corresponding
seats 28
obtained in the movable slice 22.
[95] Always referring to FIG. 10, the separation movement of said lifter 15
from the
movable slice 22 occurs through a cam eyelet 16 inside which a pin 17 slides
allowing
said lifter 15 to shift along the second T-guides 18 with variable speed
depending on
the mould kinematisms requirements.
[96] From FIG. 10 it also appears how the T-guides 18 give the movement
direction of the
side lifter 15, while the translation speed is given by the cam eyelet 16.
[97] The advantages resulting from using the moulding apparatus according to
the present
invention are evident from the description of a preferred embodiment above
depicted
in detail; in particular:
[98] - the guarantee of an excellent aesthetic quality of the produced
articles, specially
after painting, as a consequence of the increased stiffness of the mould;
[99] - the reduction of the moulding times, due to the mould compact sizes as
well as to
the decrease of the movement strokes;
[100] - the reduction of the wear caused by the sliding of the press
mechanical components
as a consequence of the provision of a puncher having a reduced weight and a
barycentre closer to the reference press-plane;
[101] - the simplification of the maintenance operations and the containment
of the relevant
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costs, thanks to the visibility of the regions subjected to wear;
[1021 - the reduction of the realisation times and the saving of material for
the mould man-
ufacturing.
[1031 It is evident that the moulding apparatus according to the present
invention, herein
disclosed by means of a preferred embodiment given by way of non limiting
example,
can be modified according to modes known to the person skilled in the art
without
departing from the scope of the present invention; in particular, the opening
and
closure system of the mould could be devised in a different way, for instance
by
employing an equipment other than a press, or the supports could be provided
with
even different systems with respect to those herein illustrated, said
arrangements being
chosen among the solutions available in the known art depending on the best
con-
structive opportunity.
[1041 Moreover, the present invention could be conveniently applied in fields
different
from the automotive one, properly adjusting the mould to shapes and sizes of
elements
used in other fields such as, for instance, furnishing, domestic appliances,
sports
equipment as well as for all those applications providing the manufacturing of
components through injection moulding.
